1. By Gordon Blake CS 46N – Jennifer Widom

2.  In 2013, there were approximately 16,121 homicides in the United States  Of those, about 11208 were committed with firearms  However, this field is under-investigated due to a ban on CDC gun violence research  Basic questions remain unanswered not for a lack of data, but rather, a need for more investigation

3. 1. How has firearm use in homicides changed over time? 1. Have guns become more or less prevalent as a murder weapon? 2. How much do rifles or large firearms account for deaths compared to handguns? 2. Which demographic indicators are most highly correlated with firearm homicides? 1. Age, gender, race? 3. How have state and federal laws in the past 15-20 years affected firearm homicides in the U.S? 1. Federal Assault Weapons Ban 2. State Conceal and Carry Laws

4. FBI Uniform Crime Report Supplementary Homicide Report CDC National Vital Statistics System Source: http://www.bjs.gov/cont ent/pub/pdf/ntmh.pdf

5. Both sets give anonymized summary statistics NVSS and SHR show slightly different numbers by very similar trends over time. Unless otherwise stated, data is this presentation is taken from the NVSS Data from both sources are not used in the same calculations in this presentation When UCR data is used in this presentation, change over time is tracked, rather than the values themselves Source: http://www.bjs.gov/content/pub/pdf/ntmh.pdf

6. 1. Data Cleaning 1. When appropriate, missing values are interpolated 1. Ex. Calculating the rate of change in firearm homicides the year after conceal and carry laws were passed 2. At other times, null values are set to zero 1. Ex. Summing the change rates in firearm homicides for all states 2. Calculations 1. Most done in Microsoft Excel 1. Percent changes in firearm homicides following the adoption of conceal and carry lays in states were done in Python 2. Rates of change and crude rates per 100,000 people were often used in place of raw values to control for population growth

7. 3. Visualizations 1. Graphs done in Microsoft Excel 1. Unless otherwise stated, X-axis is time in years 2. Maps done through Tableau 1. States with missing data or out-of-range values greyed out 3. Other visualizations done via RAW

8. 1. How has firearm use in homicides changed over time? 1. Have guns become more or less prevalent as a murder weapon? 2. How much do rifles or large firearms account for deaths compared to handguns?

9. Fifteen Year Average: Total Homicides: 17,445 Firearm Only: 11,652 Homicides Committed by Firearms: 66.8% Change Over Time: Total Homicides declined by 768 Firearm Homicides rose by 380 What’s the Spike in Total Homicide From? September 11, 2001

10. Proportion of Homicides Committed with Firearms Even as homicides have declined over the past 15 years, firearms have become a more common weapon

11. Adjusting for Population The absolute number of firearm homicides has increased over the past fifteen years by 380 However, the rate per 100,000 people fell by 0.33 over that same time period Therefore, the population has been growing faster than the firearm homicide rate

12. Large and Small Weapons According to the 2013 UCR, handguns accounted for between 68% and 91% of gun-related murders

13.  Guns are the most common means of committing homicide and have become more prevalent over the past 15 years  Handguns are the most used weapon, while the use of large firearms has declined  Despite increases in absolute numbers, murders by firearm have declined relative to the population over this time frame

14. 2. Which demographic indicators are most highly correlated with firearm homicides? 1. Age, gender, race?

15. Firearm Victims by Gender Men are overwhelmingly more likely to be victims of gun homicide than women. Most variation in the number of firearm homicides is accounted for by changes in male deaths

16. Firearm Victims by Gender Cont. Men account for about 84% of firearm deaths over the past 15 years. In the same period, men accounted for 68% of non-firearm homicide victims

17. Age Firearm homicides are most prevalent from ages 25-44 Gender The gender imbalance holds for every age bracket and race. However, at ages 65-84, the difference between genders is much smaller that for younger ages. Race Blacks and African Americans are disproportionately victims of gun violence *Rates computed out of given demographic population, not total country population

18. State Correlations The South shows the highest firearm homicide rates in the county per 100,000 people: Louisiana: 9.6 Mississippi: 7.2 Alabama: 6.6 *Greyed-out states did not have statistically significant rates ** Data from 2013

19.  Firearm homicide rates vary significantly by Age, Gender, Race, and State  Age:  Homicides most prevalent at ages 15-44  Distribution skewed right, long tail as age increases  Gender:  For all ages and races, males are more likely than females to be victims of gun violence  Ratio of approximately 84% Male and 16% Female victims has held steady over the past 15 years  Race:  Firearm homicide victims are disproportionately black and African Americans

20. 3. How have state and federal laws in the past 15-20 years affected firearm homicides in the U.S? 1. Federal Assault Weapons Ban 2. State Conceal and Carry Laws

21.  Passed into law in 1994  Banned semi-automatic rifles, pistols, and shotguns with detachable magazines and certain other characteristics including:  Folding or telescoping stock  Pistol grip  Bayonet mount  Flash suppressor, or threaded barrel designed to accommodate one  Grenade launcher mount  Expired in 2004 *Source: Wikipedia

22.  Became law in 2005  Eliminates the liability of gun manufacturers if their product is used to commit a crime  Manufacturers are still liable for defective products or negligence  Focus on gun manufacturers, not gun owners *Source Wikipedia

23. Federal Laws No long-term trend resulting from changes in federal gun laws can be immediately detected Firearm homicides appear to change cyclically independent of federal gun laws Perhaps there was a greater effect on rifles and “large firearms”…

24. Homicides Resulting from Rifles and Shotguns Rifle and shotgun rate of change is fairly similar to overall rate of change. Once again, the Federal Assault Weapons Ban appeared to have little effect on the use of large firearms in homicides

25.  Policy Types:  No-Issue: Private citizens not allowed to carry a concealed handgun in public  May-Issue: Permit required, applicant must have “good cause” to carry a handgun, granting authority may exercise discretion  Shall-Issue: Permit required, authority must issue license if applicant fulfills certain criteria  Unrestricted: No permit required to carry a concealed handgun  The specifics of these laws vary from state to state. This analysis will focus only on the changes in the above four law types Source: Wikipedia

26. Conceal and Carry Laws: Trend toward shall-issue laws over the past 30 years Data for the following four visualizations will be taken from the UCR SHS, from 1995-2014 Source: http://www.gun-nuttery.com/rtc.php

27. Conceal and Carry Laws by State: Map shows percent change in homicides one year after each state adopted Must-Issue conceal and carry laws. Green shows an increase. Red shows a decrease. Greyed-out states did not adopt the law in the time frame from 1995 to 2013 Sum of Changes: 62.2% Average 1 Year Change: 3.1 % Increase 95% Confidence Interval: [-8.3, 14.5] *Nebraska removed from calculations as an outlier

28. Conceal and Carry Laws by State: Map shows percent change in homicides three years after each state adopted Must-Issue conceal and carry laws. Green shows an increase. Red shows a decrease. Greyed-out states did not adopt the law in the time frame from 1992 to 2011 Sum of Changes: 28.5% Average 3 Year Change: 1.2% Increase *Nebraska removed from calculations as an outlier

29. Conceal and Carry Laws by State: Map shows percent change in homicides one year after each state adopted unrestricted conceal and carry laws. Green shows an increase. Red shows a decrease. Greyed-out states did not adopt the law in the time frame from 1995 to 2013 Sum of Changes: -87.1% Average 1 Year Change: -21.8% Decrease *Small sample size, only four states

30. Conceal and Carry Laws by State: Map shows percent change in homicides three years after each state adopted unrestricted conceal and carry laws. Green shows an increase. Red shows a decrease. Greyed-out states did not adopt the law in the time frame from 1992 to 2011 Sum of Changes: -56.3% Average 3 Year Change: 18.8% Decrease *Small sample size, only three states

31.  No significant change in firearm homicides resulted from either the expiration of the Federal Assault Weapons Ban or the Protection of Lawful Commerce in Arms Act  On average, states experienced a small increase in firearm homicides following the adoption of must-issue conceal and carry permits  However, this increase is much smaller than the variability of firearm homicides within states from year to year. In other words, the results are not statistically significant.  The states that did adopt unlimited conceal and carry laws experienced declines in homicide rates in the following years  However, the sample size was small (3-4 states), and the states that adopted the laws had relatively small populations, potentially inflating their rates of change.

32.  If firearm homicide records by state could be obtained for before 1995, more states could be included in the analysis of changes in the homicide rate after adoption of more permissive conceal and carry laws  Several states only recently adopted conceal and carry laws, including Maine, Kansas, and Arkansas. It will be interesting to monitor the changes in their firearm homicide rates in the coming years.